Centrifugal casting apparatus

ABSTRACT

A centrifugal casting apparatus is provided with means for supporting an article in a predetermined position with respect to a mold pattern in the casting apparatus whereby the article will be imbedded in the centrifugally cast body; counterweights are provided within the casting apparatus for compensating for the buoyancy of an article being imbedded where such article has a specific gravity that is less than the casting material.

United States Patent [191 Schroll et al.

[4 1 Jul 24, 1973 CENTRIFUGAL CASTING APPARATUS [75] Inventors: JosefSchroll; Werner Sroke, both of Rostock, Germany [73] Assignee: VEBIngenieurburo Schiifbau,

Rostock-Osthafer, Germany 22] Filed: o1.1,1971

[21] App1.No.: 185,793

[30] Foreign Application Priority Date Oct. 16, 1970 Germany WP 31b2/l50 720 Jan. 29, 1971 Germany P 21 04 148.5

[52] US. Cl. 164/287 [51] Int. CL B2211 13/00 [58] Field of Search164/286, 287, 288,

[56] References Cited UNITED STATES PATENTS 2,052,043 8/1936 Weaver164/300 X 1,552,246 9/1925 Thompson 164/332 X 1,963,400 6/1934 Campbell164/298 X Primary Examiner-J. Spencer Overholser Assistant Examiner-JohnS. Brown Attorney-Cushman, Darby & Cu shman [57] ABSTRACT A centrifugalcasting apparatus is provided with means for supporting an article in apredetermined position with respect to a mold pattern in the castingapparatus whereby the article will be imbedded in the centrifugally castbody; counterweights are provided within the casting apparatus forcompensating for the buoyancy of an article being imbedded where sucharticle has a specific gravity that is less than the casting material.

2=Claims, 1 Drawing Figure CENTRIFUGAL CASTING APPARATUS The presentinvention relates to an improved centrifugal casting apparatus, and morespecifically to an apparatus having means for positioning an article ina predetermined position with respect to the mold pattern whereby thearticle will become imbedded in the object being cast. The presentinvention further provides means for compensatingfor the differences inspecific gravities between the article being imbedded and the materialfrom which the cast article is to be made.

BACKGROUND OF THE INVENTION The superior structural quality of metalarticles that are formed by centrifugal casting has long been knownsince articles made by a centrifugal casting process may be formed withvery precise engineering tolerances and yet can be produced in largequantities at costs that are generally less than those of articles whichare formed by static casting methods.

However, when it is desired to form a cast article having a preciselylocated openings, ducts or borings, diffrculties have been encounteredin constructing suitable mold patterns for casting such articlesparticularly where it was desired to imbed objects having a specificgravity or density differing from that which the cast article is made.In particular, when it was desired to imbedhollowbodies such as tubesinto the wall of an article being cast, centrifugal castng methods couldnot be employed since it was difficult to precisely maintain thepositionof the hollow bodies with respect to the molten castingmaterial, when the casting apparatus was rotated at high speedsresulting in the creation of large centrifugal forces which'tended toseparate the hollow bodies from the casting material.

SUMMARY OF THE INVENTION The improved centrifugal casitng apparatus ofthe present invention consists in the provision of support members whichsecurely locate and maintain an article which is destined to be imbeddedin the cast article in a predetermined position with respect to the moldpattern which is formed in the centrifuge housing. By way of example,where the article being cast is a cylinder bushing and the article beingimbedded in the wall of the cylinder bushing is a cooling tube, duringthe rotation of the centrifuge, the tube, which is a hollow body, willexperience a radial force on account its lighter specific gravity ordensity with respect to the molten iron which is used to formthecylinder bushing. As the centrifuge operates, the molten metal willexperience a centrifugal force forcing it into intimate contact with thesand pattern whereas the hollow tube will become buoyant as the depth ofthe molten metal increases and surrounds the tube. To counteract suchbuoyancy and to maintain the tube in the desired position, the presentinvention provides support means including one or more counter-weightswhich are securely attached to the tube during the casting process. Themass of the counter-weights is determined by the difference in specificgravities or densities of the two articles.

' Use of the apparatus of the present invention will facilitate thecasting of pieces wherein articles may be very precisely imbedded withinsuch pieces without adversely affecting the quality of the casting.

BRIEF DESCRIPTION OF THE DRAWING In the single FIGURE, there isillustrated a cross sectional view taken along a portion of thelongitudinal axis of a generally cylindrical, centrifugal castingapparatus of the present invention.

DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawing,there is illustrated a portion of a substantially cylindricalcentrifugal casting apparatus generally designated as 10 which isadapted to cast hollow cylindrical bodies such as cylinder bushings, forexample. The apparatus 1l0 consists of a cylindrical centrifuge housing12 which is adpated to be rotated about its longitudinal axis 14. Itwill be understood, of course, that the housing 12 is formed to berotationally balanced with respect to the axis 14 whereby the axis willpass through the center of mass of the housing 12. Within the housing12, there is disposed a generally cylindrical container 16 which ismounted within housing 12 prior to the deposition of a pattern moldingmaterial as at 18 within container 16. Conventionally one end of boththe housing 12 and container 16 are closed, the pattern, molding andcasting materi als being-introduced at the other open end. The paternmolding material 18 preferably consists of packed fine grain sand, butit will be understood that other mold material may be employed. Informing a pattern in material 18 a pattern 19 (not shown) which conformsin outer dimensions and shape tothe object to be centrifugally cast (butmay be hollow) is introduced into cylinder 16 and the molding material18 is tightly packed around pattern 19 whence the pattern is removed.

Subsequent to the forming of a pattern in material 18 within the housing12, the housing 12 is then rotated by sutiable conventional means (notshown) such as rollers, gears or pulleys connected to a motor about itslongitudinal axis l4, during which rotation, molten casting material 24such as iron is gradually deposited in the interior of the mold pattern18 as through opening 20 whereby the molten material will be spreadevenly to a desired depth over the interior surface 22 of the moldpattern by virtue of the centrifugal force exerted thereon by virtue ofthe rotation of the apparatus.

When it is desired to embed an article such as a cooling tube 26 withinthe casting material 24, the present invention provides support memberssuch as at 28, 29 and 30 which at one end securely support tube 26, theother end of each support member being securely attached to base memberssuch as base member 32 for member 28, and base member 34- for members 29and 30, respectively. The material of construction of the supportmembersdepends upon the casting material since the supports will remain withinthe cast article and thus should be compatible therewith. For example,if the casting material is gray iron, support members 28 through 30 maybe conveniently fabricated from a steel containing about 0.15 percentcarbon. The base members 32 and 34 may, in turn, be positioned onlocating pads 36 and 38 which due to their shape allow the flat bottomedsupport members to be easily mounted on the curving interior surface ofmold container 16.

Themanner in which the support members 28' through 30, the basemembers32 and 34 and the locating pads 36 and 38 are assembled together willnow be discussed. V

Pattern 19 discussed above includes dowel holes into which dowels areplaced which are removable through the hollow center of pattern 19.These dowels press base members 32 and 34 against pads 36 and 38,respectively, while material 18 is being packed about pattern 19. Thedowels and pattern are then removed and the pin-like lower portions ofsupport members 28 through 30 are inserted through the holes formed inmaterial by the dowels. The pin portions may be threaded and receivedwithin threaded apertures within base members 36 and 38.

In the illustrated embodiment, the top portions of support members 28,29 and 30 are ring shaped at one end so that the cooling tube 26 may beinserted therethrough-and held as to lateral movement while yet allowinglongitudinal expansion and contraction of tube 26 during casting andcooling. It will be understood, however, that for articles of differingshapes, the various support members may be appropriately designed toretain such articles in place.

Since the volume of casting material 24 displaced by the cooling tube 26has a greater specific gravity and density than the cooling tube 26,during the centrifuging process, a bouyant force radially directedtowards the axis of rotation 14 would normally arise. To counter-balancethis bouyant force, the base members 32 and 34 are constructed from amaterial and are so arranged so as to act, in effect as counter-weightsso that the rotation equilibrium of the centrifuge housing, and castingmaterial 24 will be maintained. Of course, the base members also exceedmaterial 18 in specific gravity and thus do not tend to float upon thismaterial. F urther, sincethe base members are recovered followingcasting and do not form a portion of the cast body they do not need tobe made of a material compatible with casting material 24.

The foregoing has been a description of an illustrative embodiment ofthe principles of the present invention and it will be understood thatvarious changes and modifications may be made therein without departingfrom the spirit and scope of the present invention as defined in theappended claims.

What is claimed is:

1. In a centrifugal casting apparatus of the type having a housingmounted for rotation about an axis passing through the center of mass ofthe housing, means removably positioned within said housing forcontaining a mold forming material, said mold forming material beingspaced from said axis of rotation so that an opening is provided alongat least a portion of said axis for receiving casting material withinsaid housing, the improvement comprising support means supported by saidcontaining means for maintaining an article having a specific gravityless than the specific gravity of the casting material in apredetermined position with respect to said axis of rotation during therotation of said housing, said support means including at least onecounterweight embedded in said mold forming material forcounterbalancing the bouyancy of a said article.

2. The apparatus as claimed in claim 1 wherein said support meansfurther includes at least one support member attached at one end to saidcounterweight and extending generally radially inwardly through the moldforming material toward said axis of rotation, the other end of saidsupport member having means for securely engaging said article to holdsaid article in said predetermined position with respect to said axis.

1. In a centrifugal casting apparatus of the type having a housingmounted for rotation about an axis passing through the center of mass ofthe housing, means removably positioned within said housing forcontaining a mold forming material, said mold forming material beingspaced from said axis of rotation so that an opening is provided alongat least a portion of said axis for receiving casting material withinsaid housing, the improvement comprising support means supported by saidcontaining means for maintaining an article having a specific gravityless than the specific gravity of the casting material in apredetermined position with respect to said axis of rotation during therotation of said housing, said support means including at least onecounterweight embedded in said mold forming material forcounterbalancing the bouyancy of a said article.
 2. The apparatus asclaimed in claim 1 wherein said support means further includes at leastone support member attached at one end to said counterweight andextending generally radially inwardly through the mold forming materialtoward said axis of rotation, the other end of said support memberhaving means for securely engaging said article to hold said article insaid predetermined position with respect to said axis.